THE SUN'S HEAT.
Prof. Langley of the Allegheny observatory has made a direct comparison between the heat of the sun and that of the flame in the mouth of a Bessemer steel convertor. Estimates of the sun's temperature probably vary among themselves more than any other attempts at scientific knowledge, ranging from 10,000,000 down to 1,500 deg. We have already published in this Miscellany some late French determinations which place it below 2,000 deg. C. Prof. Langley's choice of a standard is excellent. The flame of the Bessemer convertor results from the burning of carbon, silicon, iron, and manganese within the vessels, the result of using this once novel fuel being a heat so great that the most refractory iron or steel is melted to thin fluidity and so much excess of heat imparted, that the mass will remain fluid, without further heat, a considerable time. The temperature of the flame is not known, though 4,000 or 5,000 deg. Fahr. has been suggested as an approximation. This does not vitiate Prof. Langley's experiment, for he used it merely as one of the most powerful artificial sources of light obtainable. His method was to compare its light with that of the sun by an arrangement that resembled a camera obscura, the light from the sun and the flame being repeatedly superposed upon each other. The arrangement worked admirably, and the observer was able to note the spots on the sun. He found that the intensely hot flame was like a dark spot compared to the sun's light and that the latter must be at least 2,168 times hotter than the flame. This carries the result in favor of the largest estimates. The flame of the convertor is not so hot as the melted steel from which it comes, but it offers better opportunities for observation. The steel itself as it was poured from the convertor was found to be not more than one-sixty-fourth as hot as the sun.
DEAF MUTES IN POLAND.
Mr. George Darwin has brought forward statistics to prove that the intermarriage of near relations does not have the unfavorable effect upon offspring which is commonly supposed. But the director of the Warsaw Institute for Deaf Mutes and the Blind combats this theory, and says that the registers kept at that and similar institutions support the popular opinion. The system of instruction at this asylum is very perfect. Mimic language being almost totally prohibited, the pupils are taught to understand the motion of the lips and to speak more or less distinctly; and after a four years' residence in the Institute, they generally attain in both a high degree of perfection. With great judgment the managers have made the technical instruction at the school of the best kind, so that the pupils readily find situations on leaving, and indeed there are never enough to fill all the situations offered. This appears to be the true method with students who would otherwise find themselves at a disadvantage with more favored competitors.
THE COMPASS PLANT.
The well-known dispute as to the "compass plant" has recently been settled by Mr. Meehan in a manner which recalls the opinions of judicial officers who deal with other than scientific questions. One party of observers say that this plant always points its leaves north and south, the leaf standing edgewise to the earth and the two sides facing to the east and west. This plant is found on the prairies and plains, and is known scientifically as silphium lacinatum, popularly as pilot weed, rosin weed, and turpentine weed. It stands from three to six feet high, and the trappers and Indians are said to find their way in dark nights by feeling its leaves. These assertions of polarity are denied by the other party. Mr. Meehan now says that both are right. When the leaves are young and small the pointing to the north is unmistakable, but when they become larger, are beaten down by rains, and weighted with sand and dew, they are not able to recover their lost bearings.
BALLOONS IN METEOROLOGY.